Recently there has been developed a high density recorded disc, such as a video disc, which contains a large number of revolutions of the recorded spiral path, about 10,000 per inch along the radius of the disc. One type of such recorded disc is made of a plastic material which is filled with conductive particles, i.e., conductive carbon black particles, such that the disc is thereby made conductive. This type of disc is more brittle than discs which do not contain these conductive particles.
These recorded discs of plastic material are generally flat, circular plates having information on one or both major surfaces thereof in the form of surface relief patterns formed along a spiral path or groove in a surface of the disc. These discs are formed or molded in a mold press having a pair of mold plates, at least one of which is movable toward and away from the other, and which when together form a mold cavity therebetween of a size and shape of the disc to be formed. Because of the fine dimensions of these recorded discs, many of the requirements for materials and processes used in the manufacture of these high density discs are different from those used previously to make audio discs.
During playback of these high density recorded discs, such as video discs, with a metal-tipped stylus, considerable friction is generated between the stylus and the disc surface. Therefore a means, such as the application of a surface lubricant which does not reduce the fidelity of the recording, must be provided to reduce the friction during playback. A suitable lubricant for these high density recorded discs, in addition to imparting good lubricity to the disc surface, must possess proper surface tension, adhesion to the disc surface, cohesion and elasto-hydrodynamic properties so as to form a uniform, thin film which will support the stylus at a constant height above the signal elements during playback. Also the lubricant must be stable against degradation due to wear, must resist evaporation and oxidation and have good electrical insulating properties with high dielectric strength. Additionally, the lubricant must be chemically inert to the materials of the disc itself, and possess good stability to high temperatures and high and low humidity conditions.
Therefore, in order to prevent undue wear between the disc and the stylus, a lubricant layer is applied to the disc surface, such as by evaporation, spraying from a solvent solution, or the like.
One of the preferred ways of applying the lubricant to the surface of a recorded disc is by spraying from solvent solution. However, it has been found that some of the preferred solvents for these disc lubricants are highly volatile and flammable, such that the use of these solvents, i.e., heptane, in the manufacturing environment or work place can be hazardous and unsafe. Therefore, there is a need for an improved process and apparatus for the safe supply, distribution and handling of a highly volatile and flammable liquid solvent, such as heptane, in the work environment. The fulfillment and satisfaction of this need resulted in the present invention.